Supercruise do not decrease endurance that much as afterburning.But it still decrease endurance/range significantly comparing to economic cruise.I thought advantages of being able to supercruise without afterburners increases endurance, not having to dump fuel into the afterburner. I suppose it's more to do with engine output than with design. Is there any information as to when China will complete WS-13E - that extra 1,000lb of dry thrust might push FC-31 to Mach 1.5-8
Advantage of supercruise :
1 it will increase the speed of the weapon you fire. So you can hit target further and quicker. Especially when you use a parabola-trajectory missile or gliding guided bomb.
2 engage and disengage quickly. it may outran enemy‘s missile, or precisely speaking reduce its effective range.
I do not know any information about WS-13E. Engine is probably the most difficult sub-system of all.
I doubt it can push FC-31 to mach 1.5 without afterburning.